This invention relates to a direct injected engine for an outboard motor and more particularly to an improved direct injection system for a two cycle internal combustion engine.
Two cycle engines are widely used, particularly in applications where high specific outputs and relatively uncomplicated, simple engine constructions are desirable. Thus, two cycle engine are frequently employed as the power plant in an outboard motor because of the small space available in the powerhead of such engines and the demand for relatively high performance.
However, because of environmental concerns, there is a desire to significantly improve the performance of two cycle engines particularly in the area of exhaust emission control. One particularly advantageous method for reducing unburned hydrocarbons in the exhaust system without sacrificing engine performance is through the use of direct cylinder injection. However, because of the fact that the engine fires every revolution of the crankshaft, and because of the overlap between the scavenging and the exhaust portions of the cycle, there is a danger that the fuel will pass out of the exhaust port.
Also, the injection rates basically must be somewhat higher with two cycle engines and four cycle engines because of the fact that there is generally less time during which the fuel can be injected. This makes it more difficult to insure that all of the injected fuel will be sufficiently vaporized to burn completely.
With two cycle engines, it is also desirable to provide some method for cooling the head of the piston. In normal crankcase compression type engines where fuel is introduced through the crankcase chamber, the fuel on the underside of the piston head can function to cool it. However, this cooling is not available with direct injected engine.
It is, therefore, a principal object of this invention to provide an improved combustion chamber configuration for a direct injected two cycle engine.
It is a further object of this invention to provide a combustion chamber arrangement for a two cycle engine wherein the fuel injector will spray in a manner to afford good fuel vaporization and still avoid fuel from passing out of the exhaust port.
It is a further object of this invention to provide an combustion chamber configuration and fuel injection system for a two cycle engine wherein the injector sprays in a manner so as to deposit some fuel on the head of the piston so as to assist in cooling of the piston.
It is a further object of this invention to provide an improved combustion chamber configuration for a direct injected two cycle engine wherein the fuel injector is mounted in the cylinder head and in such a manner as to ensure that fuel will not impinge upon areas of the cylinder head or on the spark plug.
This invention is adapted to be embodied in a two cycle internal combustion engine operating on a crankcase compression principal. The engine has a combustion chamber that is defined by a cylinder bore of a cylinder block, a piston reciprocating in that cylinder bore and a cylinder head closing the cylinder bore and having a recessed area cooperating with the piston and cylinder bore to form the combustion chamber of the engine. At least one scavenge port opens into one side of the cylinder bore and is opened and closed by the reciprocation of the piston therein. At least one exhaust port is also formed in the cylinder bore and is opened and closed by the reciprocation of the piston. The at least one scavenge port and at least one exhaust port are disposed in diametrically opposed relationship. A fuel injector is mounted in the cylinder head and has its injection tip extending into the cylinder head recess for spraying fuel into the combustion chamber. The fuel injector is positioned generally on the side of the combustion chamber where the exhaust port is located. The fuel injector sprays generally downwardly and toward the at least one scavenge port and has a spray pattern that is configured so that it will not impinge upon the cylinder head recessed surface area.